U.S. Pat. No. 5,080,056 issued Jan. 15, 1992 describes a practice of applying thermal spray aluminum bronze wear-resistant coatings on the cylinder bore portion of an aluminum engine block casting. The need for the application of such wear-resistant coatings arises from the fact that aluminum alloys such as aluminum alloy 319, which are particularly suitable for casting complex engine block castings, do not necessarily provide wear resistance against the pistons reciprocating at high speed in the cylinders of the engine.
Our copending application, U.S. Ser. No. 938,528 describes a practice for cleaning and surface roughening metal substrate surfaces preparatory to the deposition of adherent thermal spray metal coatings. That practice is now preferred for use in the deposition of suitable wear-resistant thermal spray metal alloy coatings to cylinder wall surfaces of cast aluminum alloy engine blocks. In such coating of internal surfaces of the complexly configured engine block castings, it is also necessary to provide for the handling of the casting to facilitate the cooling of the block during application of the hot coating and to prevent deposit of the coating where it is not wanted.
It is an object of the present invention to provide a method for the application of a thermal spray coating to the cylinder wall portions of a cast aluminum automotive engine block so as to minimize the need for masking of the cylinder block and to avoid thermal damage to the block from the hot metal droplets that form the coating.
It is a further object of the present invention to provide a method for applying thermal spray, wear-resistant coatings such as aluminum bronze alloys or suitable steel alloys to the cylinder wall portions of an engine block which utilizes the cooling passages of the block to preheat the block preparatory to applying the coating and to cool the block during the coating process.
It is a still further object of the present invention to provide apparatus for the cooling of a cast aluminum engine block and the application of a thermal spray metal coating which does not require masking of the block to prevent overspray into regions of the block not intended to be coated.
In accordance with a preferred embodiment of our invention, these and other objects are accomplished as follows.